Vacuum pressure fill of viscous dampers

ABSTRACT

Method and apparatus for filling viscous dampers in which the method comprises assembling a damper housing with an inertia weight placed loosely therewithin and a housing top having a single aperture therein and adapted to provide a complete closure for the inertia weight, placing the assembly in a vacuum chamber equipped with an electron beam welding device and means for effecting relative movement between the assembly and the electron beam welding device, and inserting a valve and fitting sealingly within said aperture with the valve in an open position, evacuating the vacuum chamber to provide a vacuum within the chamber and within the damper assembly, effecting movement between the assembly and the device to sealingly weld the top to the damper housing, closing the valve, attaching means for supplying a viscous fluid under pressure to said valve, removing the valve from the damper assembly, and welding a plug within the aperture to sealingly retain the fluid within. The apparatus comprises a vacuum chamber, an electron beam welding device mounted for welding within said chamber, means for positioning a viscous damper assembly within said chamber, said damper assembly comprising a damper housing and a cover therefor with an inertia weight disposed therewithin, said damper assembly also comprising a single aperture for filling the damper with a viscous fluid, means for evacuating the vacuum chamber and damper assembly disposed within, means for providing a relative movement between said assembly and said welding device for effecting a complete weld between the housing and cover, and means for filling the welded assembly through said aperture.

This a division of Ser. No. 477,914, filed June 10, 1974, now U.S. Pat.No. 3,939,880.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for fillingviscous dampers, and more particularly to a method and apparatus forfilling viscous dampers in which the fabrication of the dampers includean electron beam welding step.

Torsional vibration dampers which comprise an inertia weight carried ina viscous fluid such as silicone are well known, and the presentinvention relates to a method and apparatus for making such dampers andin particular to a method of filling said dampers with viscous fluid. Inaccordance with prior methods, the damper was completely securedtogether by welding or the like with the inertia weight enclosedtherein, and with the top of the housing being provided with two holes.These holes are utilized for filling, with one of the holes beingpresent to provide for egress of air and the other of the two holesbeing present to provide for entering of the viscous fluid. It is veryimportant that the viscous damper be filled with viscous fluid andsubstantially no air be present within the housing in order to assureproper operation of the damper assembly when absorbing torsionalvibrations and the like. It is also advantageous to utilize electronbeam welding in the fabrication of the damper as set forth more fully inCanadian Pat. No. 878,847 issued Aug. 24, 1971 for Torsional VibrationDamper.

In view of the high viscosity fluid being placed within the damperassembly, and the close clearances likely to be present between theinertia weight and the housing wall in certain locations during filling,it is difficult to force viscous fluid into the damper housing and fillthe space therein. However, it is important to positively assure thatall of the air that might otherwise be present within the housing in thecompleted unit be removed, and that the interior be sealed so as toretain the interior of the housing free from trapped air and the likewhich would interfere with the proper operation of the damper. Thepresent invention is directed to an improved method of making andfilling said dampers in which improvements are provided both withrespect to the simplicity of processing and reliability of manufacture.

SUMMARY OF THE INVENTION

In accordance with the present invention, torsional vibration dampers ofthe character described are filled by evacuating the housing to removesubstantially all of the air therein, supplying a viscous fluid througha single aperture to fill the evacuated space within the housing, andsealingly securing a plug in said aperture to provide a completeairtight viscous fluid-filled housing interior.

Thus, the present invention utilizes a single aperture for removal ofair from within the housing and for filling the housing with viscousfluid. In this way, the manufacture of the device is simplified byutilizing only one aperture for filling and therefore requiring only oneaperture to be plugged in the final fabrication step. In addition, theuse of a single aperture for filling provides for a simple qualitycontrol with respect to the sealing relation of the housing itself,because any tendency of air to leak into the housing during the fillingstep can be easily detected. Therefore, the method of the inventionprovides the simple quality control in fabricating the viscous damper inaccordance with the invention.

In addition, the method of this invention provides for a simplifiedprocess of making viscous dampers by utilizing a step of providing avacuum for two different purposes. In other words, in the preferredmethod of making a viscous damper in accordance with this invention, thedamper housing and top is sealingly secured by electron beam welding ina vacuum chamber. The vacuum, which is utilized for the electron beamwelding process, is also utilized to provide the vacuum within theinterior of the welding housing incident to the filling operationdescribed above.

Thus in a preferred method, the housing is finally secured by electronbeam welding to provide a sealed interior, with the electron beamwelding taking place within an evacuated vacuum chamber. Prior toeffecting the welding step, the housing is assembled with the inertiaweight therein, and a valve is placed in a single aperture provided inthe damper housing. The valve is left open so as to assure that theevacuaction of the vacuum chamber will also provide evacuation for theinterior of the damper housing. The electron beam welding is theneffected, and the valve is closed. The vacuum chamber may then beallowed to assume normal atmospheric pressure, and the valve is attachedto a source of viscous fluid with the attachment being made in such away that no air is present between the valve connection and the viscousfluid source. The valve is then opened and the viscous fluid is forcedinto the interior of the housing through the aperture with the vacuumwithin the housing assisting in bringing the viscous fluid intoposition, and assuring that the housing is filled with viscous fluid.

Since the housing should be completely sealed after the welding iscompleted, the time required to fill the device with viscous fluid willbe relatively constant, unless a leak is present that would allow air toenter the interior of the housing. In such a case, the apparent fillingwould not occur during the expected time period and the malfunctionwould be obvious to the operator.

It should be noted that an important characteristic of the method ofthis invention is the utilization of a single aperture for removing airand supplying viscous fluid to the interior of the damper housing. Itmay also be noted that it is generally conventional to provide theaperture at the top of the housing for easy application of a product forsealing the interior. However, it will be appreciated that the use of asingle aperture allows the aperture to be placed in the housing itself,and it may be advantageous to provide the aperture somewhere on the sideof the damper housing instead of within the lid. This relocation is madepossible by virtue of the single aperture and the fact that a singleaperture may be located on the side of the housing and still be orientedto the uppermost position of the unit during subsequent operationalsteps.

In its apparatus form, the apparatus comprises a vacuum chamber equippedwith means for effecting electron beam welding in accordance withconventional electron beam welding procedures. The apparatus alsocomprises means for effecting relative movement between the damperhousing and the electron beam welding apparatus so that the welding maybe accomplished in all of the areas which are to be welded. In otherwords, a typical damper will have an annular chamber carrying aring-shaped inertia weight, and a cover or top which is in the form of aflat disk adapted to complete the annular space within and provide aflange for attachment to the vehicle in the usual way. With thisconstruction, the cover will be welded onto the annular housing by twoconcentric circular welds with one on each side of and at the top of theannular space within the housing.

The means for effecting relative rotation between the electron beamwelding device and the damper, is preferably constructed to provide forrotation of the damper with respect to the electron beam welding device.In order to move to the second circular weld, the electron beam weldingdevice is then displaced laterally and rotation of the housing againeffected so that the two concentrically disposed circular welds may beformed. The apparatus also will comprise a valve having a fittingadapted to sealingly fit into the aperture provided in the damperhousing or cover, pump means operatively connected to a source ofviscous fluid to be provided within the housing and a suitable passageleading from the pump means to said valve.

In the preferred method utilizing the apparatus specifically describedherein, the aperture is placed on the housing cover, and the valve isprovided with a handle disposed to be actuated by the electron beamwelding device at the termination of the welding operation, wherebyautomatic closing of the valve occurs within the vacuum chamber. Inaccordance with this procedure, however, with the the valve in the coverof the device, it is necessary to have the hose from the supply sourceof viscous fluid removed from the valve in order to allow proper weldingto occur on each side of the valve. However, this hose is easilyconnected and disconnected as required. It will be appreciated that thevalve could be placed in an aperture located in the side of the housingwhere the connection to the filling device could be retained at alltimes. With such an arrangement, the valve could be a three positionvalve whereby the interior of the housing is communicated to theinterior vacuum chamber in one position, the valve shut-off in thesecond position, and the valve communicating to the supply source instill another position. In such a case, the valve would be actuated atthe end of the welding step to shut off the valve, the chamber openedand the valve turned on. Alternatively, a two-position valve could beprovided, in which a shut-off position is not utilized, but instead thevalv is switched from the communication to the interior of the vacuumchamber to the supply source upon completion of the welding operation.With such an arrangement, the filling could take place entirely withinthe vacuum chamber, or other variations in the process could beprovided. In this last procedure any leaks in the damper housing wouldbecome apparent because fluid would migrate therethrough to reach theevacuated chamber. Accordingly, all of these operational variations areto be construed to be within the ambit of the present invention.

It is thus seen that a primary object of the present invention is toprovide an improved method and apparatus for filling vibrational torsiondampers with viscous fluid in which the filling operation is carried outin a simplified and more reliable manner.

Another object of the invention is to provide a method and apparatus forfilling and making viscous dampers in which a single aperture isutilized for filling and in which only said single aperture needs to beplugged up in the final assembly step to achieve complete sealing.

A further object of the invention is to provide a method of makingviscous dampers in which quality control is built into the procedurewhereby simplified production of reliable dampers is positively assured.

Further objects and features of advantage of the invention will becomeapparent as the specification progresses.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the invention is illustrated in the accompanyingdrawings forming part of this description, in which:

FIG. 1 is a perspective view of an apparatus of the invention with aviscous damper shown in place therein and with certain of the partsbeing broken away to show interior elements;

FIG. 2 is a fragmentary side elevational view of a portion of theapparatus in its operative stage showing the viscous damper in section;and

FIG. 3 is a fragmentary isometric view of the finally plugged portion ofthe damper.

While only the preferred form of the invention is shown, it should beunderstood that various changes or modifications may be made within thescope of the claims attached hereto without departing from the spirit ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring more particularly to the drawings, there is shown in FIG. 1 anapparatus 10 constructed in accordance with the invention. The apparatuscomprises a vacuum chamber 11, formed by a housing 12, and various otherconventional structures (not shown) generally associated with vacuumchambers such as exhaust pumps, and the like. The chamber is equippedwith rails 13 and 14 for supporting a wheeled table 15 and for allowingmovement of the table into and out of the chamber 11. Table 15 comprisesa rotatable pedestal 16 mounted thereon and journalled therethrough withits lower end connected to a spur gear 17 provided for rotating thepedestal 16. A spur gear 18 is provided in vacuum chamber 11 andpositioned to engage the spur gear 17 as the table is brought intooperative position. Spur gear 18 is journalled through the floor of thevacuum chamber and connected to a power source (not shown). A rack 19 isalso provided on the underside of table 15, with the rack engaging spurgear 20, which is also journalled through the floor of the vacuumchamber and externally powered for moving the table into position withinthe vacuum chamber.

The apparatus 10 also comprises an electron beam welding device 21mounted on suitable frame members 22 within the vacuum chamber 11. Thiswelding device operates in a vacuum and provides a welding operationthat has the advantages of deep penetration and elimination ofdistortion all without the use of additional welding materials.

The apparatus 10 is constructed to receive a torsional vibration damperassembly 23 on the pedestal 16 as shown in FIG. 1. The torsionalvibration damper assembly 23 comprises a main housing 24 which isgenerally U-shaped in cross section and provides an annular chamber 25therewithin. The main housing 24 also has an internally extending flange26 formed as shown to provide a flat upper surface in contact with top27. The top 27 and flange 26 are equipped with suitable bore holes 28for securing the device in place on the crankshaft of a vehicle or atany other desired location. An inertia weight 29 is provided within theannular chamber 25, and this completes the assembly as it is provided invacuum chamber 11. However, it should be noted that the top 27 of thetorsional vibration damper assembly 23 also comprises an aperture 30,and that this aperture is the only opening communicating between theinterior and exterior of the damper assembly.

The apparatus 10 also comprises a valve 31 equipped with a suitablefitting adapted to fit sealingly within aperture 30. As here shown,valve 31 is a three-position valve communicating in one position to anorifice 32, in a second position shut-off, and in the third position, toa conduit 33; said positioning being effected by handle 34.

The apparatus 10 also comprises a container 35 having an outlet hose 36adapted to fit onto conduit 33. A conduit 37, is also provided to supplyviscous fluid into the chamber 35 under pressure by means of a pump (notshown), so that the fluid may be moved through hose 36, conduit 33,valve 31, aperture 30 and into annular chamber 25.

The operation of the apparatus shown in FIG. 1 is substantially asfollows:

Torsional vibration damper assembly 23 is positioned on the rotatablepedestal 16 and wheeled into vacuum chamber 11 on rails 14. When rackgear 19 reaches engagement with spur gear 20, the table may be driventhrough spur gear 20 into position. Once the operating position isachieved, gears 18 and 17 will come into engagement and the electronbeam welding device 21 will be in a beginning position to weld the top27 onto the main housing 24. It should be noted that the torsionalvibration damper assembly 23 has valve 31 sealingly placed in aperture30 and with the valve open so that orifice 32 is in communication to theinterior annular chamber 25 of the damper assembly 23.

With the damper assembly thus in position in the vacuum chamber 21, thechamber is sealed and evacuated in order to provide a vacuum therein.This vacuum not only exists within the chamber, but also within theannular chamber 25 of damper assembly 23 so as to simultaneously providea vacuum within the damper assembly while providing a vacuum forelectron beam welding. The electron beam welding operation is thencarried out to provide a circular weld along circle 38 as shown in FIG.1 to secure top 27 of the damper assembly to the flange 26 of the mainhousing. The beam is moved laterally and welding is then directed aroundedge 39 to secure the outer portion of top 27 to the main housing 24.This welding completely integrates the top 27 into the housing 24, andprovides a single sealed unit, except for aperture 30.

It will be noted that electron beam welding device 21 is equipped withan actuating member 40 positioned to contact handle 34 and close valve31. Each of the circular welds is achieved by electron beam 41positioned to strike the appropriate circle and by driving gear 18,which in turn rotates gear 17 and rotatable pedestal 16 to provide thedesired rotation to the torsional vibration damper assembly 23. Eachweld circle may be conducted simultaneously, or separately, from twodifferent beam sources. Alternatively, two weld circles can be made froma single beam by means, such as an air cylinder (not shown), for movingthe beam 41 laterally from one circular position to the other.

After the welding has been completed and the valve shut-off, the vacuumchamber is allowed to assume atmospheric pressure and the outlet hose 36is secured to conduit 33 to supply viscous fluid into valve 31. It isimportant in making this connection that no trapped air be present inthe conduit or in the hose, so that the complete contact of viscousfluid is made right up to the valve member in communication with thevacuum within annular chamber 25. With the connection thus made, valve31 is positioned to communicate with container 35 and viscous fluid isforced under pressure into the chamber 25. It will be noted, that thevacuum in chamber 25 not only solves the problem of air removaltherefrom during filling, but also assists in bringing in the viscousfluid and enabling it to fill all of the close-fitting spaces.

It will also be appreciated that a quality control is apparent to theoperator at this point, because any leaks would destroy the vacuuminside the vibration damper assembly. This would change the apparentfilling time and alert the operator to be aware of an imperfect unit.

Thus, it is seen that the apparatus 11 is utilized in partially carryingout the filling method and in making a viscous damper according to theinvention, and that the method is used to complete the overall fillingoperation. In its method aspect, the manufacture of the damper assemblyis continued after filling by removal of the valve 31, and welding of aplug 42 into the aperture 30 as illustrated in FIG. 3.

In the foregoing description, it is seen that an improved method offilling the viscous dampers is provided in which the filling method isincorporated into a procedure for making the damper itself with economyof fabrication steps being achieved together with advantageous results.Specifically, the method of this invention provides improvements in themanner of handling of trapped air and positively assures the absence ofany substantial amount of air within the completed damper assembly. Thisis particularly important in certain damper articles which containsynthetic coatings on the inertia weight, which coatings are subject tocorrosion caused by air. Thus an anaerobic surrounding is desirable forthese types of structures. The removal of air contact by evacuation ofair prior to the filling with viscous fluid is advantageous in assuringcomplete removal of contacting air and avoidance of continued contact ofair with said coatings after assembly. The invention is alsoparticularly applicable to improvements in making damper assemblieswhich are already known and proven to be eminently satisfactory fortheir intent and purpose, because the method is in no way dependent uponthe specific shape or materials utilized in the damper assembly itself.

From the above description it is seen that an improved method of fillingviscous dampers is provided together with an improved method andapparatus for making viscous dampers employing this filling method. Itis also seen that said improved method provides an economy ofconstruction together with improved reliability in the fabricationprocess.

What is claimed is:
 1. A method of making a viscous damper, comprising the steps ofplacing a damper assembly into a vacuum chamber, said damper assembly comprising a housing, an inertial weight, and a housing cover, with the housing and cover having a single aperture therein, and providing a complete enclosure except for said aperture, evacuating the chamber and the space around the inertia weight within the damper housing, welding the cover onto the housing in said evacuated chamber, pumping a viscous fluid through the aperture and into the evacuated space within the damper assembly to fill said space with viscous fluid, and sealingly securing a plug in said aperture.
 2. A method of making a viscous damper as defined in claim 1, which also comprises the steps of placing a valve and fitting therefor sealingly within the aperture, and operating the valve to provide a communication between the space within the damper assembly and the vacuum chamber to assure evacuation of the space as the chamber is evacuated.
 3. A method of making a viscous damper as defined in claim 2, in which the welding step is carried out by an electron beam welding process.
 4. A method of making a viscous damper as defined in claim 2, in which the aperture is located in the housing cover. 